Substrate free LED package

ABSTRACT

A method of fabricating a substrate free light emitting diode (LED), includes arranging LED dies on a tape to form an LED wafer assembly, molding an encapsulation structure over at least one of the LED dies on a first side of the LED wafer assembly, removing the tape, forming a dielectric layer on a second side of the LED wafer assembly, forming an oversized contact region on the dielectric layer to form a virtual LED wafer assembly, and singulating the virtual LED wafer assembly into predetermined regions including at least one LED. The tape can be a carrier tape or a saw tape. Several LED dies can also be electrically coupled before the virtual LED wafer assembly is singulated into predetermined regions including at the electrically coupled LED dies.

CLAIM OF BENEFIT TO PRIOR APPLICATIONS

This Application is a continuation of U.S. patent application Ser. No.13/619,886, entitled “Substrate Free LED Package”, filed Sep. 14, 2012,which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention generally relates to a chip package and a methodof manufacturing the same, and more particularly to a light emittingdiode (LED) chip package without a substrate and a method ofmanufacturing the same.

Background

LED chips emit light in response to excitation by an electrical current.One typical LED includes a heterostructure grown on a substrate bymetal-organic vapor phase epitaxy or similar techniques. An LEDheterostructure includes n and p type semiconductor layers that sandwichlight producing layers. Exemplary light producing layers may be quantumwells surrounded by barrier layers. Typically, electrical contacts areattached to n and p semiconductor cladding layers. When a forward biasis applied across electrical contacts, electrons and holes flow from nand p layers into a light producing active region. Light is producedwhen these electrons and holes recombine with each other in an activeregion comprising at least one semiconductor material.

LED chips are typically enclosed in a package that extracts the lightand protects the chip from being damaged. The LED package typicallyincludes phosphors that convert light generated by the LED into whitelight, a lens that directs light, contact pads for electricallyconnecting the LED package to an external circuit, as well as othercomponents. The cost of packaging the LED chip can significantlycontribute to the overall cost of making an LED device and is thereforean important factor into whether LED devices can be made commerciallyviable for consumers.

Therefore, there is a need for an LED device that can be manufacturedand packaged in high volumes and delivered to consumers at low cost.

SUMMARY OF THE INVENTION

Accordingly, embodiments are directed to a substrate free LED packageand method of manufacturing the same that substantially obviates one ormore of the problems due to limitations and disadvantages of the relatedart.

Embodiments provide techniques for fabricating substrate free LEDdevices in high volumes at low cost with fewer process steps whilemaintaining high LED performance, consistent color uniformity, and highmanufacturing yields. The techniques for fabricating these substratefree LED devices reduce the fabrication costs associated with packagingLED devices making them more affordable and more likely to be adopted byconsumers. These techniques include packaging substrate free LED chips,and provide processes that permit high design flexibility by eliminatingdie attach and wire bonding processes used in LED packaging.

In one embodiment, a method of fabricating a substrate free LED includesarranging LED dies on a tape to form an LED wafer assembly, molding anencapsulation structure over at least one of the LED dies on a firstside of the LED wafer assembly, removing the tape, forming a dielectriclayer on a second side of the LED wafer assembly, forming an oversizedcontact region on the dielectric layer to form a virtual LED waferassembly, and singulating the virtual LED wafer assembly intopredetermined regions including at least one LED. The tape can be acarrier tape or a saw tape. In one embodiment a protective film can beformed over the encapsulation structure.

In another embodiment, the tape on which the LED dies are arranged is acarrier tape. In this embodiment, a pick and place procedure is used todo the arrangement of the LED dies. Before arranging the LED dies on thecarrier tape, this embodiment can further include, placing a waferhaving LED dies on the saw tape, singulating the LED dies by cutting thewafer completely through and partially cutting the saw tape to a depthless than the thickness of the saw tape, and expanding the saw tape toincrease the spacing between the singulated LED dies. In one embodiment,each of the LED dies that are arranged on a carrier tape can beconfigured to emit light at a wavelength, where the variation inwavelengths between dies disposed on the carrier tape ranges from about0 nm to about 2.5 nm relative to each other.

In yet another embodiment, the tape on which the LED dies are arrangedis a saw tape. This embodiment can further include disposing a waferhaving LED dies on the saw tape, singulating the LED dies by cutting thewafer completely through and partially cutting the saw tape to a depthless than the thickness of the saw tape, and expanding the saw tape toincrease the spacing between the singulated LED dies.

In yet another embodiment, molding an encapsulation structure includesforming a phosphor loaded silicon material over the LED dies.

In yet another embodiment, molding an encapsulation structure includesmolding a lens selected from the group consisting of a flat lens, a domelens, or a Fresnel lens.

In another embodiment, a method of fabricating a substrate free LEDincludes arranging LED dies, which include die contacts, on a tape toform an LED wafer assembly, molding an encapsulation structure over atleast one of the LED dies on a first side of the LED wafer assembly,removing the tape to expose the die contacts, forming a dielectric layeron a second side of the LED wafer assembly, electrically coupling atleast one die contact from a first die with at least one die contactfrom a second die, forming an oversized contact region on the dielectriclayer to form a virtual LED wafer assembly, and singulating the virtualLED wafer assembly into predetermined regions including at least theelectrically coupled first die and second die. The tape can be a carriertape or a saw tape. In one embodiment, a protective film can be formedover the encapsulation structure.

In another embodiment where at least two dies are electrically coupledto each other before the virtual LED wafer assembly is singulated, thetape on which the LED dies are arranged is a carrier tape. In thisembodiment, a pick and place procedure is used to arrange the LED dieson the carrier tape. Before arranging the LED dies on the carrier tape,this embodiment can further include, disposing a wafer having LED dieson the saw tape, singulating the LED dies by cutting the wafercompletely through and partially cutting the saw tape to a depth lessthan the thickness of the saw tape, and expanding the saw tape toincrease the spacing between the singulated LED dies. In one embodiment,each of the LED dies that are arranged on a carrier tape can beconfigured to emit light at a wavelength, where the variation inwavelengths between dies disposed on the carrier tape ranges from about0 nm to about 2.5 nm relative to each other.

In yet another embodiment, where at least two dies are electricallycoupled to each other before the virtual LED wafer assembly issingulated, the tape on which the LED dies are arranged is a saw tape.This embodiment can further include disposing a wafer having LED dies onthe saw tape, singulating the LED dies by cutting the wafer completelythrough and partially cutting the saw tape to a depth less than thethickness of the saw tape, and expanding the saw tape to increase thespacing between the singulated LED dies.

In another embodiment, a substrate free LED includes an LED die havingat least one contact, a dielectric layer formed on a first side of theLED, an oversized contact region on the dielectric layer, and anencapsulation structure on a second side of the LED die. The oversizedcontact region is electrically coupled to the at least one contact.

In yet another embodiment, the dielectric layer of the substrate freeLED includes a Distributed Bragg Reflector (DBR) which has a high indexof refraction dielectric material adjacent to a low-index of refractiondielectric material.

In yet another embodiment, the oversized contact region of the substratefree LED includes a fan out structure.

In yet another embodiment, the oversized contact region of the substratefree LED includes a portion that extends to an end of the LED diethrough the dielectric layer.

In yet another embodiment, the oversized contact region of the substratefree LED includes at least one of Al, Ag, Rh, Pd, Cu, Au, Cr, Ti, W, andNi.

In yet another embodiment, the substrate free LED includes at least oneof a vertical LED structure with electrical on the same side, lateralLED structure, flip chip, or thin-film LED structure.

In yet another embodiment, the substrate free LED includes a protectivefilm formed on the LED structure.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1A is an exemplary flow chart illustrating the formation of asubstrate free LED package where packaging operations are performed ondies disposed on saw tape, according to embodiments.

FIG. 1B is an exemplary flow chart illustrating the formation of asubstrate free LED package where packaging operations are performed ondies disposed on carrier tape, according to embodiments.

FIG. 2A illustrates a wafer with LED dies placed on saw tape, bothbefore and after the saw tape has been expanded, according toembodiments.

FIG. 2B illustrates a diced LED wafer with LED dies, disposed on sawtape that has been expanded, and LED dies that have been picked andplaced from the saw tape onto a carrier tape where they will undergosubstrate free LED packaging, according to embodiments.

FIGS. 3A-3C illustrate a cross-sectional view of a substrate free LEDpackage having a flat lens structure, at various stages of thefabrication process, according to an embodiment.

FIG. 3D illustrates a bottom view of the substrate free LED packagehaving flat lens structure after singulation, according to embodiments.

FIGS. 4A-4C illustrate a cross-sectional view of a substrate free LEDpackage having a dome lens structure, at various stages of thefabrication process, according to another embodiment.

FIG. 4D illustrates a bottom view of the substrate free LED packagehaving a dome lens structure after singulation, according toembodiments.

FIGS. 5A-5C illustrate a cross-sectional view of a substrate free LEDpackage having at least two dies electrically coupled together aftersingulation, at various stages of the fabrication process, according toanother embodiment.

FIG. 5D illustrates a bottom view of the substrate free LED packagehaving at least two dies electrically coupled together aftersingulation, according to embodiments.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Various aspects of the invention will be described herein with referenceto drawings that are schematic illustrations of idealized configurationsof the present invention. As such, variations from the shapes of theillustrations resulting from manufacturing techniques, tolerances, etc.,are to be expected. Thus, the various aspects of the invention presentedthroughout this disclosure should not be construed as limited to theparticular shapes of elements (e.g., regions, layers, sections,substrates, etc.) illustrated and described herein, but are to includedeviations in shapes that result, for example, from manufacturing. Byway of example, an element illustrated or described as a rectangle mayhave rounded or curved features and/or a gradient concentration at itsedges rather than a discrete change from one element to another.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the drawings. It will be understoodthat relative terms are intended to encompass different orientations ofan apparatus in addition to the orientation depicted in the drawings. Byway of example, if an apparatus in the drawings is turned over, elementsdisclosed as being on the “lower” side of other elements would then beoriented on the “upper” side of the other elements. The term “lower” cantherefore encompass both an orientation of “lower” and “upper,”depending on the particular orientation of the apparatus. Similarly, ifan apparatus in the drawing is turned over, elements described as“below” or “beneath” other elements would then be oriented “above” theother elements. The terms “below” or “beneath” can therefore encompassboth an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andthis disclosure.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise,”“comprises,” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof. The term “and/or” includesany and all combinations of one or more of the associated listed items.

Various disclosed aspects may be illustrated with reference to one ormore exemplary configurations. As used herein, the term “exemplary”means “serving as an example, instance, or illustration,” and should notnecessarily be construed as preferred or advantageous over otherconfigurations disclosed herein.

Furthermore, various descriptive terms used herein, such as “on” and“transparent,” should be given the broadest meaning possible within thecontext of the present disclosure. It will be understood that when anelement such as a region, layer, section, substrate, or the like, isreferred to as being “on” another element, it can be directly on theother element or intervening elements may also be present. In contrast,when an element is referred to as being “directly on” another element,there are no intervening elements present. In addition, something thatis described as being “transparent” should be understood as having aproperty that allows no significant obstruction or absorption ofelectromagnetic radiation in the particular wavelength (or wavelengths)of interest, unless a particular transmittance is provided. It will befurther understood that when an element is referred to as being “formed”on another element, it can be grown, deposited, etched, attached,connected, coupled, or otherwise prepared or fabricated on the otherelement or an intervening element.

Embodiments provide techniques for fabricating substrate free LEDdevices in high volumes at low cost with fewer process steps whilemaintaining high LED performance, consistent color uniformity, and highmanufacturing yields. The techniques for fabricating these substratefree LED devices reduces the fabrication costs associated with packagingLED devices, making them more affordable and more likely to be adoptedby consumers. These techniques include packaging substrate free LEDchips and provide processes that permit high design flexibility byeliminating die attach and wire bonding processes used in LED packaging.

FIG. 1A is an exemplary flow chart 100A illustrating the formation of asubstrate free LED package where packaging operations are performed ondies disposed on saw tape. The process starts in operation 101A, where asubstrate is provided for epitaxially forming a light emitting diode(LED). In operation 102A, an epitaxial layer, e.g., gallium nitride, isformed via metal-organic chemical vapor deposition (MOCVD) or molecularbeam epitaxy (MBE), as known in the art, on the substrate. The substratemay be made of any material, such as, for example, sapphire, silicon,silicon carbide, gallium nitride, aluminum nitride, or the like.

In operation 104A, wafer fabrication techniques are used to form an LEDwafer assembly. The LED wafer assembly may include at least one of avertical LED structure with electrical contacts on the same side,lateral LED structure, flip chip, or thin-film LED structure. Examplesof the wafer fabrication techniques that are known in the art includephotolithography, doping, etching, and other semiconductor processingtechniques. At the end of operation 104A, an LED wafer assembly includesa plurality of LED dies, e.g., one hundred or more LED dies havingassociated electrical contacts and light emitting regions. In oneembodiment, the wafer assembly is further described with reference toU.S. Pat. No. 7,781,780, which is hereby incorporated by reference as iffully set forth herein.

Optionally operation 106A may be performed after operation 104A. Inoperation 106A, the LED wafer assembly is probed and tested by acomputerized probing device for the purpose of associating X and Yvalues with each die, e.g., wavelength tested in order to determine awavelength of each die and distribution across the wafer. For example,during the probing process, each die is energized and variouscharacteristics are determined, e.g., wavelength, lumen output, voltage,current, and any other operating parameters are collected and associatedwith each die. In one embodiment, the measured parameters for each dieare mapped to X and Y values based on at least one of thesecharacteristics. Thus, each die is associated with its own X and Yvalues prior to singulation.

Next, in operation 108A, mounting and singulation processes areperformed on the LED wafer assembly to divide the LED wafer assembly.The LED wafer assembly is mounted onto a saw tape and then cut intoindividual dies. The cutting process singulates the dies into individualdies without cutting all the way through the saw tape. This processleaves the dies attached to the saw tape, which is expandable, in thesame configuration that the dies were on the wafer. By singulating theLED dies on the saw tape and expanding the saw tape in operation 110A,the individual LED dies are spaced apart further from each other thanthey are on the wafer. Increasing the spacing between the LED dies makesit easier to perform packaging steps on the separated LED dies, asdescribed with reference to FIGS. 3-5 below. This expansion operation110A can be performed by stretching the saw tape having the LED diesmounted thereon to a predetermined size.

An example of saw tape is the PROFILM™ DU177E product manufactured byAdvantek, Inc. with Global Operation Headquarters in Calamba City,Philippines. Other examples of saw tape can be used that are known tothose skilled in the art. In one embodiment, the singulation isperformed using front-side laser scribing to scribe the LED waferassembly into individual LED dies. The scribing is performed to a depththat does not cut all the way through the saw tape. In anotherembodiment, the wafer is mounted onto the saw tape and the dies aresingulated into groups of dies or arrays. Afterwards, each group of diesor arrays is then processed as illustrated in FIGS. 3-5.

In operation 112A, the LED dies, which are disposed on the expanded sawtape, are packaged using substrate free packaging techniques. Thesubstrate free packaging techniques are used to encapsulate the LED die,form a phosphor and/or lens on the LED die, form contacts to the LED dieleads, make electrical connections, etc., as described in further detailwith reference to FIGS. 3-5. Encapsulation includes encapsulating theLED dies in a transparent encapsulation material such as transparentsilicone. Alternatively, other transparent materials such as transparentacrylic materials including, for example, poly(methyl methacrylate) PMMAor polycarbonate can be used. The encapsulation material may be used toextract the light emitted from the LED dies, as well as protect the LEDdies. By encapsulating the LED dies, they become extremely durable withno loose or moving parts. Singulation includes cutting the dies from thesaw tape into a group having a predetermined number of dies or intoindividual dies.

As described herein, the substrate free LED processing of operation 112Ais used to form a virtual LED wafer assembly or substrate free LEDpackage.

Next in operation 114A, a test and sort operation is used to test thepackaged LEDs and sort the packaged LEDs. Testing the LEDs can includetesting for resistance, light output, efficiency, etc. Sorting can bedone according to any predetermined testable parameters such asresistance, light output, efficiency, etc. The process ends in operation120A after the LED dies are tested and sorted.

FIG. 1B is another exemplary flow chart 100B illustrating the formationof a substrate free LED package where packaging operations are performedon LED dies disposed on carrier tape, according to another embodiment.Operations 101B, 102B, 104B, 106B, 108B, and 110B are similar tooperations 101A, 102A, 104A, 106A, 108A, and 110A described above withreference to FIG. 1A. Briefly, in operation 101B a substrate is providedfor epitaxially forming a light emitting diode (LED), in operation 102Ban epitaxial layer is formed on the substrate, in operation 104B waferfabrication techniques are used to form an LED wafer assembly, inoperation 106B probing and testing are optionally performed on the LEDdies, in operation 108B the wafer is mounted onto a saw tape and the LEDdies are singulated, and in operation 110B the saw tape with the LEDdies mounted thereon is expanded. Since operations 101B, 102B, 104B,106B, 108B, and 110B are substantially the same as operations 101A,102A, 104A, 106A, 108A, and 110A, further details regarding operations101B, 102B, 104B, 106B, 108B, and 110E are provided with reference toFIG. 1A.

In operation 111B, a pick and place procedure is performed on theindividual LED dies. During the pick and place procedure, LED dies thatare disposed on the expanded saw tape are picked off the expanded sawtape and disposed onto a carrier tape. As part of this pick and placeprocedure, the LED dies are sorted and binned and can be placed on thecarrier tape in an order different from their order on the saw tape. Inone embodiment, the X and Y values determined during operation 106B areused to bin the LED dies according to desired characteristics. In oneembodiment, the LED dies are sorted and binned in groups such that theLED dies within a group each have a wavelength difference between theLED dies that is less than 2.5 nm. These LED dies are then mounted on anew carrier tape to form a wafer assembly having similar wavelengthcharacteristics. An example of carrier tape is the SPV-224/214 productmanufactured by Nitto Denko Corporation of Osaka, Japan. Other examplesof carrier tape that are known to those skilled in the art can be used.The characteristics or wavelengths may be configured as desired.

In operation 112B, the LED dies, which are disposed on the carrier tape,are packaged using substrate free packaging techniques. The substratefree packaging techniques are used to encapsulate the LED die, form aphosphor and/or lens on the LED die, form contacts to the LED die leads,make electrical connections, etc., as described in further detail withreference to FIGS. 3-5. Next, in operation 114B, a test and sortoperation substantially similar to the test and sort operation describedin operation 114A is used to test the packaged LEDs and sort thepackaged LED dies. Testing the packaged LED dies can include testing forcharacteristics such as light output, correlated color temperature(CCT), color rendering index (CRI), voltage across contacts, etc.Sorting can be done according to any predetermined testable parameterssuch as resistance, light output, efficiency, etc. The process ends inoperation 120B after the LED dies are tested and sorted.

FIG. 2A illustrates a wafer placed on saw tape both before and after thesaw tape has been expanded. The left illustration on FIG. 2A shows anLED wafer 218A, which includes LED dies 204A, mounted on a saw tape 211Abefore the saw tape 211A has been expanded. During operations, the LEDwafer 218A is mounted onto a saw tape 211A and then cut into individualdies. The cutting process singulates the dies 204A into individual dieswithout cutting all the way through the saw tape 211A. This processleaves the dies 204A attached to the saw tape 211A, which is expandable,in the same configuration that the dies 204A were on the wafer 218A. Theright side of FIG. 2A shows an LED wafer 218A, which includes LED dies204A, mounted on a saw tape 211A after the saw tape 211A has beenexpanded. By singulating the LED dies 204A on the saw tape 211A andexpanding the saw tape 211A, as is further described with reference tooperation 110A, the individual LED dies 204A are spaced further apartfrom each other than they are on the wafer. Increasing the spacingbetween the LED dies 204A makes it easier to perform packaging steps onthe separated LED dies. In one embodiment, the singulation is performedby front-side laser scribing the LED wafer assembly into individual LEDdies 204A. The scribing is performed to a depth that does not cut allthe way through the saw tape 211A. In another embodiment, the LED wafer218A is mounted onto the saw tape 211A, and the LED dies 204A aresingulated into groups of dies or arrays. Each group of dies or array isthen processed as illustrated in FIGS. 3-5.

FIG. 2B illustrates a diced LED wafer 238B with LED dies 224B, disposedon saw tape 231B that has been expanded, and LED dies 224B that havebeen picked and placed from the saw tape 231B onto a carrier tape 241Bwhere they will undergo substrate free LED packaging, according toembodiments. The left illustration on FIG. 2B shows an LED wafer 238B,which includes LED dies 224B, mounted on a saw tape 231B after the sawtape 231B has been expanded. As explained with reference to FIG. 2A,during operations, the LED wafer assembly 238B is mounted onto a sawtape 231B, cut into individual dies 224B and then expanded by expandingthe saw tape 231B. The cutting process singulates the LED dies 224B intoindividual dies without cutting all the way through the saw tape 231B.This process leaves the LED dies 224B attached to the saw tape 231B,which is expandable, in the same configuration that the LED dies 224Bwere on the wafer 238B. The right side of FIG. 2B shows the LED dies 224after they have been picked and placed from the saw tape 231B onto acarrier tape 241B. The LED dies 224B will undergo substrate free LEDpackaging while they are disposed on the carrier tape 241B. The pick andplace procedure is described in further detail with reference tooperation 111B, in FIG. 1B. After the LED dies 224B are picked andplaced onto the carrier tape, the LED dies 224B undergo substrate freeLED packaging as described in further detail with reference to FIGS. 1Band 3-5.

FIGS. 3A-3C illustrate a cross-sectional view of a substrate free LEDpackage having a flat lens structure, at various stages of thefabrication process, according to an embodiment. FIG. 3D illustrates abottom view of the substrate free LED package having flat lens structureafter singulation, according to embodiments.

FIGS. 3A-3D, illustrate the substrate free LED process by generallydepicting an LED structure being packaged at various stages as describedin FIGS. 1A-1B at operations, 112A, and 112B. More specifically, withreference to FIG. 1A, the substrate free fabrication process may beperformed at operation 112A after the mounting and singulation operation108A and the expansion operation 110A. Alternatively, as illustrated inFIG. 1B, the substrate free fabrication process may be performed atoperation 112E after the pick and place operation 111B.

In FIG. 3A, the LED wafer assembly 302 includes LED dies 304 that caninclude at least one of a vertical LED structure with electricalcontacts on the same side, lateral LED structure, flip chip, orthin-film LED structure. In this embodiment, the LED wafer assembly 302includes a plurality of LED dies 304 each having die contacts 306. TheLED dies 304 are mounted on tape 324, which can be either saw tape, asdescribed in operation 112A, or carrier tape, as described in operation112B. An example of saw tape is the PROFILM™ DU177E product manufacturedby Advantek, Inc. with Global Operation Headquarters in Calamba City,Philippines. An example of carrier tape is the SPV-224/214 productmanufactured by Nitto Denko Corporation of Osaka, Japan. Other examplesof saw tape and carrier tape can be used that are known to those skilledin the art.

An encapsulation structure 308, which is formed over the LED dies 304,is formed by molding the encapsulation materials on the LED dies 304 andtape 324. The shape of the encapsulation structure 308 is illustrated asbeing a flat conformal structure but can have other shapes, as describedwith reference to FIGS. 4A-4D. In one embodiment, the encapsulationstructure 308 includes a transparent silicone layer of molded lensesformed over the LED dies 304. In another embodiment, the encapsulationstructure 308 includes a silicone layer having suspended phosphorparticles formed over the LED dies 304. In still another embodiment, theencapsulation structure 308 includes a layer of conformal phosphorformed over the LED dies 304. The encapsulation structure 308 may alsoinclude a textured surface as described with reference to U.S. PatentApplication Publication Nos. 2011/0089457, 2011/0025191, 2011/0026263,and 2011/0089454, each of which is hereby incorporated by reference.FIG. 3A further illustrates a protective film 311 formed on theencapsulation structure 308. The protective film 311 includes a moldrelease film such as the FLUON® ETFE product manufactured by Asahi GlassCo., Ltd. of Tokyo, Japan. Other mold release films can be used that areknown to those skilled in the art.

In FIG. 3B, the LED wafer assembly 302 includes the plurality of LEDdies 304 each having die contacts 306, encapsulation structure 308,dielectric layer 310, protective film 311, via 312, and an oversizedcontact region 316. The tape 324, which can be saw tape or carrier tape,is removed. During the formation of the wafer assembly illustrated inFIG. 3B, an etching or cleaning process is optionally performed toremove any impurities. The dielectric layer 310, the via 312, and theoversized contact region 316 are formed after the tape 324 is removedand the optional etching and/or cleaning processes are performed. Thedielectric layer 310, can optionally include a Distributed BraggReflector (DBR) structure. The DBR structure may be fabricated using aseries of alternating high index/low index dielectric materials. Aseries of 2 pairs of ¼λ SiO₂ and ¼λ TiO₂ over a layer of 1¾λ SiO₂ isused to enhance the reflectivity at lower angles. A DBR structure usesoptical interference to affect reflectivity; as a result, theirthickness is more critical than the thickness of the underlying thickSiO₂ layer.

In one embodiment, the dielectric layer 310 is a DBR having amulti-layer stack structure using a combination of high and lowrefractive index materials. In an embodiment, the two materials chosenhave indices of refraction that are as different as possible to maximizethe reflectivity of a stack over all angles. Chosen materials alsoshould have very low absorption at the wavelength emitted by the LED. Inanother embodiment, a high-index material is TiO₂ and a lower indexmaterial is SiO₂. Materials suitable for high index layers are titaniumdioxide (TiO₂), Ti₃O₅, Ti₂O₃, TiO, ZrO₂+TiO₂ZrO₂Nb₂O₅, CeO₂, ZnS, Al₂O₃,niobium pentoxide (Nb₂O₅), and tantalum pentoxide (Ta₂O₅). Suitable lowindex materials include SiO, SiO₂, and MgF₂. In some embodiments, lowand/or high refraction index materials may be polymers such as siloxanepolymers or others known to one knowledgeable in the art.

In one embodiment, the thicknesses of DBR layers are odd multiples ofquarter wavelengths. In an embodiment, a two layer combination, or pair,of high n_(H)/low n_(L) index of refraction materials is repeated atleast twice, giving a four layer structure of high n_(H)/low n_(L)/highn_(H)/low n_(L). The DBR layers may be deposited using evaporation,physical vapor deposition, atomic layer deposition (ALD), or otherwell-known techniques in the art. The DBR may be formed as describedwith reference to U.S. Pat. No. 7,622,746, which is hereby incorporatedby reference.

The dielectric layer 310 is formed with vias 312 disposed therein. Thevia 312 is configured to electrically couple the die contact 306 of theLED die 304 to the oversized contact region 316. In one embodiment, thevia 312 has a surface area that is smaller than the surface area of thedie contact 306. In another embodiment, the via 312 has a surface areathat is equivalent to the surface area of the die contact 306. The via312 and the oversized contact region 316 may be formed from conductivematerials such as, for example, Al, Ag, Rh, Pd, Cu, Au, Cr, Ti, W, andNi, and their alloys. The die contact 306 can be formed from conductivematerials such as, for example, Al, Ag, Rh, Pd, Cu, Au, Cr, Ti, W, andNi, and their alloys. Once the wafer assembly 302 has been processed, asshown in FIG. 3B, the wafer assembly is considered to be a virtual LEDwafer or substrate free LED package because it is ready for dicing, asillustrated with reference to FIG. 3C.

FIG. 3C is an illustration showing a singulation process that isperformed on the virtual LED wafer assembly to form a functional LEDsubstrate free package. In one embodiment, singulation is performed byusing a dicing saw that divides the virtual LED wafer assembly intoindividual dies or LED substrate free packages as shown along lines 318.Optionally, the LED substrate free package may be probe tested andbinned prior to or after singulation.

The oversized contact region 316 is patterned to be oversized or have afanned shape, e.g., fan out structure, as shown in FIG. 3D. A fan outstructure can include any structure that expands the surface area of aprimary electrical contact to make it easier to make external electricalconnections to the primary electrical contact. FIG. 3D is anillustration showing the fan out structure fabricated using theoperations described above with reference to FIGS. 3A-3C. The oversizedcontact region 316 can be patterned to extend over the edge of the dieand extend to about half of the die size, without making contact withother contact regions of opposite polarity, as shown in FIG. 3D. Theoversized contact region 316 may include any type of geometric pattern.

FIGS. 4A-4C illustrate a cross-sectional view of a substrate free LEDpackage having a dome lens structure, at various stages of thefabrication process, according to another embodiment. FIG. 4Dillustrates a bottom view of the substrate free LED package having adome lens structure after singulation, according to embodiments.

FIGS. 4A-4D, illustrate the substrate free LED process by generallydepicting an LED structure having a dome shaped lens being packaged atvarious stages as described in FIGS. 1A-1B at operations, 112A, and112B. More specifically, with reference to FIG. 1A, the substrate freefabrication process may be performed at operation 112A after themounting and singulation operation 108A and the expansion operation110A. Alternatively, as illustrated in FIG. 1B, the substrate freefabrication process may be performed at operation 112B after the pickand place operation 111B.

In FIG. 4A, the LED wafer assembly 402 includes LED dies 404 that caninclude at least one of a vertical LED structure with electricalcontacts on the same side, lateral LED structure, flip chip, orthin-film LED structure. In this embodiment, the LED wafer assembly 402includes a plurality of LED dies 404 each having die contacts 406. TheLED dies 404 are mounted on tape 424, which can be either saw tape, asdescribed in operation 112A, or carrier tape, as described in operation112B. An example of saw tape is the PROFILM™ DU177E product manufacturedby Advantek, Inc. with Global Operation Headquarters in Calamba City,Philippines. An example of carrier tape is the SPV-224/214 productmanufactured by Nitto Denko Corporation of Osaka, Japan. Other examplesof saw tape and carrier tape can be used that are known to those skilledin the art.

An encapsulation structure 408, which is formed over the LED dies 404,is formed by molding the encapsulation materials on the LED dies 404 andtape 424. The shape of the encapsulation structure 408 is illustrated asbeing a curved structure such as a dome shape or hemispherical shape.However, the structure can have other shapes as described herein withreference to the other FIGS. 1A-5D. In one embodiment, the encapsulationstructure 408 includes a transparent silicone layer of molded lensesformed over the LED dies 404. In another embodiment, the encapsulationstructure 408 includes a silicone layer having suspended phosphorparticles formed over the LED dies 404. In still another embodiment, theencapsulation structure 408 includes a layer of conformal phosphorformed over the LED dies 404. The encapsulation structure 408 may alsoinclude a textured surface as described with reference to U.S. PatentApplication Publication Nos. 2011/0089457, 2011/0025191, 2011/0026263,and 2011/0089454, each of which is hereby incorporated by reference.FIG. 4A further illustrates a protective film 411 formed on theencapsulation structure 408. The protective film 411 includes a moldrelease film such as the FLUON® ETFE product manufactured by Asahi GlassCo., Ltd. of Tokyo, Japan. Other mold release films, which are known tothose skilled in the art, can also be used.

In FIG. 4B, the LED wafer assembly 402 includes the plurality of LEDdies 404 each having die contacts 406, curved encapsulation structure408, dielectric layer 410, protective film 411, contact 412, and anoversized contact region 416. The tape 424, which can be saw tape orcarrier tape, is removed. During the formation of the wafer assemblyillustrated in FIG. 4B, an etching or cleaning process is optionallyperformed to remove any impurities. The dielectric layer 410, thecontact 412, and the oversized contact region 416 are formed after thetape 424 is removed and the optional etching and/or cleaning processesare performed. The dielectric layer 410, can optionally include aDistributed Bragg Reflector (DBR) structure. The DBR structure may befabricated using a series of alternating high index/low index dielectricmaterials. A series of 2 pairs of ¼λ SiO₂ and ¼λ TiO₂ over a layer of1¾λ SiO₂ is used to enhance the reflectivity at lower angles. A DBRstructure uses optical interference to affect reflectivity; as a result,their thickness is more critical than the thickness of the underlyingthick SiO₂ layer.

In one embodiment, the dielectric layer 410 is a DBR having amulti-layer stack structure using a combination of high and lowrefractive index materials. In an embodiment, the two materials chosenhave indices of refraction that are as different as possible to maximizethe reflectivity of a stack over all angles. Chosen materials alsoshould have very low absorption at the wavelength emitted by the LED. Inanother embodiment, a high-index material is TiO₂ and a lower indexmaterial is SiO₂. Materials suitable for high index layers are titaniumdioxide (TiO₂), Ti₃O₅, Ti₂O₃, TiO, ZrO₂+TiO₂ZrO₂Nb₂O₅, CeO₂, ZnS, Al₂O₃,niobium pentoxide (Nb₂O₅), and tantalum pentoxide (Ta₂O₅). Suitable lowindex materials are SiO, SiO₂, and MgF₂. In some embodiments, low and/orhigh refraction index materials may be polymers such as siloxanepolymers or others known to one knowledgeable in the art.

In one embodiment, the thicknesses of DBR layers are odd multiples ofquarter wavelengths. In an embodiment, a two layer combination, or pair,of high n_(H)/low n_(L) index of refraction materials is repeated atleast twice, giving a four layer structure of high n_(H)/low n_(L)/highn_(H)/low n_(L). The DBR layers may be deposited using evaporation,physical vapor deposition, atomic layer deposition (ALD), or otherwell-known techniques in the art. The DBR may be formed as describedwith reference to U.S. Pat. No. 7,622,746, which is hereby incorporatedby reference.

The dielectric layer 410 is formed with vias 412 disposed therein. Thevia 412 is configured to electrically couple the die contact 406 of theLED die 404 to the oversized contact region 416. In one embodiment, thevia 412 has a surface area that is smaller than the surface area of thedie contact 406. In another embodiment, the via 412 has a surface areathat is equivalent to the surface area of the die contact 406. The via412 and the oversized contact region 416 may be formed from conductivematerials such as, for example, Al, Ag, Rh, Pd, Cu, Au, Cr, Ti, W, andNi, and their alloys. The die contact 406 can be formed from conductivematerials such as, for example, Al, Ag, Rh, Pd, Cu, Au, Cr, Ti, W, andNi, and their alloys. Once the wafer assembly 402 has been processed, asshown in FIG. 4B, the wafer assembly is considered to be a virtual LEDwafer or substrate free LED package because it is ready for dicing, asillustrated with reference to FIG. 4C.

FIG. 4C is an illustration showing a singulation process that isperformed on the virtual LED wafer assembly to form a functional LEDsubstrate free package. In one embodiment, singulation is performed byusing a dicing saw that divides the virtual LED wafer assembly intoindividual dies or LED substrate free packages as shown along lines 418.Optionally, the LED substrate free package may be probe tested andbinned prior to or after singulation.

The oversized contact region 416 is patterned to be oversized or have afanned shape, e.g., fan out structure, as shown in FIG. 4D. FIG. 4D isan illustration showing the fan out structure fabricated using theoperations described above with reference to FIGS. 4A-4C. The oversizedcontact region 416 can be patterned to extend over the edge of the dieand extend to about half of the die size, without making contact withother contact regions of opposite polarity. The oversized contact region416 may be of any type of geometric pattern.

FIGS. 5A-5C illustrate a cross-sectional view of a substrate free LEDpackage having at least two dies electrically coupled together aftersingulation, at various stages of the fabrication process, according toanother embodiment. FIG. 5D illustrates a bottom view of the substratefree LED package having at least two dies electrically coupled togetherafter singulation, according to embodiments.

FIGS. 5A-5D, illustrate the substrate free LED process by generallydepicting an LED structure being packaged at various stages as describedin FIGS. 1A-1B at operations, 112A, and 112B. More specifically, withreference to FIG. 1A, the substrate free fabrication process may beperformed at operation 112A after the mounting and singulation operation108A and the expansion operation 110A. Alternatively, as illustrated inFIG. 1B, the substrate free fabrication process may be performed atoperation 112B after the pick and place operation 111B.

In FIG. 5A, the LED wafer assembly 502 includes a plurality of LED dies504 that can include at least one of a vertical LED structure withelectrical contacts on the same side, lateral LED structure, flip chip,or thin-film LED structure. In this embodiment, the LED wafer assembly502 includes a plurality of LED dies 504 each having die contacts 506.The LED dies 504 are mounted on tape 524, which can be either saw tape,as described in operation 112A, or carrier tape, as described inoperation 112B. An example of saw tape is the PROFILM™ DU177E productmanufactured by Advantek, Inc. with Global Operation Headquarters inCalamba City, Philippines. An example of carrier tape is the SPV-224/214product manufactured by Nitto Denko Corporation of Osaka, Japan. Otherexamples of saw tape and carrier tape can be used that are known tothose skilled in the art.

An encapsulation structure 508, which is formed over the LED dies 504,is formed by molding the encapsulation materials on the LED dies 504 andtape 524. The shape of the encapsulation structure 508 can be a flatconformal structure, dome structure, or other lens structure. The shapeof the encapsulation structure 508 is illustrated as being a dome shapein FIG. 5A. In one embodiment, the encapsulation structure 508 includesa transparent silicone layer of molded lenses formed over the LED dies504. In another embodiment, the encapsulation structure 508 includes asilicone layer having suspended phosphor particles formed over the LEDdies 504. In still another embodiment, the encapsulation structure 508includes a layer of conformal phosphor formed over the LED dies 504. Theencapsulation structure 508 may also include a textured surface asdescribed with reference to U.S. Patent Application Publication Nos.2011/0089457, 2011/0025191, 2011/0026263, and 2011/0089454, each ofwhich is hereby incorporated by reference. FIG. 5A further illustrates aprotective film 511 formed on the encapsulation structure 508. Theprotective film 511 includes a mold release film such as the FLUON® ETFEproduct manufactured by Asahi Glass Co, Ltd. of Tokyo, Japan. Other moldrelease films can be used, as known to those skilled in the art.

In FIG. 5B, the LED wafer assembly 502 includes the plurality of LEDdies 504 each having die contacts 506, encapsulation structure 508,dielectric layer 510, protective film 511, contact 512, and oversizedcontact region 516. The tape 524, which can be saw tape or carrier tape,is removed. During the formation of the wafer assembly illustrated inFIG. 5B, an etching or cleaning process is optionally performed toremove any impurities. The dielectric layer 510, the contact 512, andthe oversized contact region 516 are formed after the tape 524 isremoved and the optional etching and/or cleaning processes areperformed. The dielectric layer 510 can optionally include a DistributedBragg Reflector (DBR) structure. The DBR structure may be fabricatedusing a series of alternating high index/low index dielectric materials.A series of 2 pairs of ¼λ SiO₂ and ¼λ TiO₂ over a layer of 1¾λ SiO₂ isused to enhance the reflectivity at lower angles. A DBR structure usesoptical interference to affect reflectivity; as a result, theirthickness is more critical than the thickness of the underlying thickSiO₂ layer.

In one embodiment, the dielectric layer 510 is a DBR having amulti-layer stack structure using a combination of high and lowrefractive index materials. In an embodiment, the two materials chosenhave indices of refraction that are as different as possible to maximizethe reflectivity of a stack over all angles. Chosen materials alsoshould have very low absorption at the wavelength emitted by the LED. Inanother embodiment, a high-index material is TiO₂ and a lower indexmaterial is SiO₂. Materials suitable for high index layers are titaniumdioxide (TiO₂), Ti₃O₅, Ti₂O₃, TiO, ZrO₂+TiO₂ZrO₂Nb₂O₅, CeO₂, ZnS, Al₂O₃,niobium pentoxide (Nb₂O₅), and tantalum pentoxide (Ta₂O₅). Low indexmaterials are SiO, SiO₂, and MgF₂. In some embodiments, low and/or highrefraction index materials may be polymers such as siloxane polymers orothers known to one knowledgeable in the art.

In one embodiment, the thicknesses of DBR layers are odd multiples ofquarter wavelengths. In an embodiment, a two layer combination, or pair,of high n_(H)/low n_(L) index of refraction materials is repeated atleast twice, giving a four layer structure of high n_(H)/low n_(L)/highn_(H)/low n_(L). The DBR layers may be deposited using evaporation,physical vapor deposition, atomic layer deposition (ALD), or otherwell-known techniques. The DBR may be formed as described with referenceto U.S. Pat. No. 7,622,746, which is hereby incorporated by reference.

The dielectric layer 510 is formed with vias 512 disposed therein. Thevias 512 are configured to electrically couple the die contact 506 ofthe LED die 504 to the oversized contact region 516. The oversizedcontact region 516 is configured to electrically couple at least two LEDdies 504 to each other by electrically coupling the die contacts 506 onthe two LED dies 504. In one embodiment, the via 512 has a surface areathat is smaller than the surface area of the die contact 506. In anotherembodiment, the via 512 has a surface area that is equivalent to thesurface area of the die contact 506. The via 512 and the oversizedcontact region 516 may be formed from conductive materials such as, forexample, Al, Ag, Rh, Pd, Cu, Au, Cr, Ti, W, and Ni, and their alloys.Once the wafer assembly 502 has been processed, as shown in FIG. 5B, thewafer assembly is considered to be a virtual LED wafer or substrate freeLED package because it is ready for dicing, as illustrated withreference to FIG. 5C.

FIG. 5C is an illustration showing a singulation process that isperformed on the now formed virtual LED wafer assembly to form afunctional LED substrate free package. In one embodiment, singulation isperformed by using a dicing saw that divides the virtual LED waferassembly into individual dies or LED substrate free packages, as shownalong lines 518. Optionally, the LED substrate free package may be probetested and binned prior to or after singulation. Once the virtual LEDwafer assembly is singulated along lines 518, the each resulting LEDpackage includes at least two LED dies 504 electrically coupled throughthe via 512 and the oversized contact region 516. Although FIG. 5C showsthat an array having two electrically coupled LED dies will be formed ifthe LED substrate package is cut along lines 518, arrays with moreelectrically coupled LED dies can be formed if the cut lines 518 aremade in other areas.

The oversized contact region 516 can be patterned to be oversized orhave a fanned shape, e.g., fan out structure, as shown in FIG. 5D. FIG.5D is an illustration showing the fan out structure fabricated using theoperations described above with reference to FIGS. 5A-5C. The oversizedcontact region 516 can be patterned to extend over the edge of the dieand extend to about half of the die size, without making contact withother contact regions of opposite polarity, as shown in FIG. 5D. Theoversized contact region 516 may include any type of geometric pattern.

The inventions and methods described herein can be viewed as a whole, oras a number of separate inventions that can be used independently ormixed and matched as desired. All inventions, steps, processes, devices,and methods described herein can be mixed and matched as desired. Allpreviously described features, functions, or inventions described hereinor by reference may be mixed and matched as desired.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of fabricating a substrate free lightemitting diode (LED), comprising: disposing a wafer having a pluralityof LED dies on a saw tape in a particular order; using a pick and placeprocedure to arrange the plurality of LED dies on a carrier tape to forman LED wafer assembly, wherein the plurality of LED dies are arranged onthe carrier tape by grouping the LED dies such that each LED die withina group has a wavelength difference between LED dies that is within apredetermined threshold value, and wherein the LED wafer assembly isformed based on the grouping of the LED dies such that the LED dies ineach group are all arranged on the carrier tape in a different orderfrom the particular order on the saw tape; molding an encapsulationstructure over at least one of the plurality of LED dies on a first sideof the LED wafer assembly; removing the tape; and singulating the LEDwafer assembly into predetermined regions comprising at least one LED.2. The method of claim 1, further comprising singulating the pluralityof LED dies by cutting the wafer completely through and partiallycutting the saw tape to a depth less than a thickness of the saw tape;and expanding the saw tape to increase spacing between the singulatedplurality of LED dies.
 3. The method of claim 1, wherein the molding ofthe encapsulation structure comprises molding a phosphor loaded siliconmaterial over the plurality of LED dies.
 4. The method of claim 1,wherein the molding of the encapsulation structure comprises molding alens selected from the group consisting of a flat lens, a dome lens, ora Fresnel lens.
 5. The method of claim 1, further comprising forming adielectric layer on a second side of the LED wafer assembly.
 6. A methodof fabricating a substrate free light emitting diode (LED), the methodcomprising: disposing a wafer having a plurality of LED dies on a sawtape; arranging the plurality of LED dies from the saw tape onto acarrier tape to form an LED wafer assembly, wherein the plurality of LEDdies are arranged on the carrier tape by grouping the LED dies such thateach LED die within a group has a wavelength difference between LED diesthat is within a predetermined threshold value; molding an encapsulationstructure over at least one of the plurality of LED dies on a first sideof the LED wafer assembly; removing the carrier tape; forming adielectric layer on a second side of the LED wafer assembly; forming anoversized contact region on the dielectric layer; and singulating theLED wafer assembly into regions that each comprise at least one LED. 7.A method of fabricating a substrate free light emitting diode (LED),comprising: disposing a wafer having a plurality of LED dies on a sawtape in a particular order; using a pick and place procedure to arrangethe plurality of LED dies on a carrier tape to form an LED waferassembly, the plurality of LED dies comprising die contacts, wherein theplurality of LED dies are arranged on the carrier tape by grouping theLED dies such that each LED die within a group has a wavelengthdifference between LED dies that is within a predetermined thresholdvalue, and wherein the LED wafer assembly is formed based on thegrouping of the LED dies such that the LED dies in each group are allarranged on the carrier tape in a different order from the particularorder on the saw tape; molding an encapsulation structure over at leastone of the plurality of LED dies on a first side of the LED waferassembly; removing the tape to expose the die contacts; electricallycoupling at least one die contact from a first die with at least one diecontact from a second die; and singulating the LED wafer assembly intopredetermined regions comprising at least the electrically coupled firstdie and second die.
 8. The method of claim 7, further comprisingsingulating the plurality of LED dies by cutting the wafer completelythrough and partially cutting the saw tape to a depth less than athickness of the saw tape; and expanding the saw tape to increasespacing between the singulated plurality of LED dies.
 9. The method ofclaim 7, further comprising: forming a dielectric layer on a second sideof the LED wafer assembly; and forming an oversized contact region onthe dielectric layer.